In typical present day hand grenades, the outer shell of the grenade is made of serrated steel sections welded together that holds a pyrotechnic fuse mechanism, which is surrounded by a high explosive material. The grenade has a filling hole for pouring in the high explosive material.
The firing mechanism is triggered by a spring-loaded striker inside the grenade. Normally, the striker is held in place by a striker lever, which is held in place by a safety pin, usually a cotter pin. The striker lever is held against the body of the grenade and when the pin is pulled out, the firing mechanism is triggered by the spring-loaded striker inside the grenade. With the pin removed, there is nothing holding the striker lever back, which means there is nothing restraining the striker from striking the blasting cap that initiates the delay column which burns slowly. In about four seconds, the delay material burns all the way through igniting the high explosive material that blows the grenade apart.
If for any reason one of the pyrotechnic components are activated, unintentionally, such as by extreme heat or by penetration of a bullet or fragment it inevitably causes the grenade to explode. Unintended explosion of a hand grenade can cause fatal injuries. If large numbers of grenades are stored in a single or enclosed storage area and if a grenade unintentionally explodes, the entire storage area could explode and cause great damage.
The aforementioned safety consideration imposes constraints on the storage and transportation of hand grenades and puts the personnel in vicinity of hand grenades at risk. It is also a waste of resources, which may be needed at any time.
The requirement for a safety measure to prevent inadvertent detonation is well known. It is also known to have a second safety measure to prevent inadvertent withdrawal of the safety pin. Thus, U.S. Pat. No. 3,865,027 relates to a hand grenade with a second safety measure. U.S. Pat. No. 3,823,670 relates to double headed cotter pin safety device. U.S. Pat. No. 5,886,288 discloses a safety pin that can be restored if circumstances warrant. FR 2 500 620 discloses a complex safety mechanism for a grenade. EP 1 548 394 A1 discloses an auxiliary safety mechanism for a grenade including a reversible slider element interposed between the delay detonator and the rest of the explosive train wherein the slider element is maintained under tension by the safety lever. Thus the safety mechanism is dependent on the safety lever, and any damage thereof will void this auxiliary safety mechanism.